1. Field of the Invention
The present invention relates to a process for removing residues from a substrate by treating that substrate with a rinse solution comprising water and at least one selected water-soluble corrosion inhibitor. In particular, the present invention relates to a process for removing a photoresist layer and certain residues from a semiconductor substrate that comprises the steps of removing the photoresist layer from the substrate, preferably with a remover solution, and then removing the residues from the substrate with a rinse solution that comprises water and at least one selected water-soluble corrosion inhibitor.
2. Brief Description of the Art
The manufacture of semiconductor components and integrated circuits is generally carried out using photolithographic processes. These processes involve first coating the semiconductor substrates with photoresist (positive or negative) to form a photoresist layer thereon, followed by imagewise exposing and subsequent developing to form a patterned photoresist layer on the substrate. This patterned layer acts as a mask for actual substrate patterning processes such as etching, doping, coating with metals or other semiconductor materials or other insulating materials.
After these substrate patterning operations, the patterned photoresist structure or layer must be removed from the substrate. In the past, mixtures of polar organic solvents with other compounds such as alkanolamines were used to strip this photoresist layer from the substrates. These solutions are commonly known in the art as photoresist stripping solutions. While these stripping solutions are generally effective, in some cases a small amount of photoresist residue and stripping solution may remain on the surface of the substrate after the stripping operation.
Alternatively, and more preferred at the present time, oxygen gas plasma ashing is used to remove the photoresist layer. This plasma treatment burns the photoresist layer; however, a small amount of photoresist residue, post-etch residue and cleaner solution may remain on the surface of the substrate in some situations.
Other methods for removing the patterned photoresist layer include mechanical means such as scrubbing with a liquid or a gas jet-stream, cryogenic treatment with liquid nitrogen, argon, or supercritical fluids, or by peeling away the layer with an adhesive-coated paper attached to the top of the photoresist layer.
When a liquid photoresist stripper solution or an oxygen gas plasma ashing step was used to remove the patterned photoresist layer, it was common to employ a subsequent liquid rinse operation. Generally, this rinse treatment involved first rinsing the substrate with an organic solvent (e.g., most commonly isopropyl alcohol) followed by a second rinsing operation with deionized water. Besides isopropyl alcohol, specific teachings of alternative organic solvent rinse solutions are described in U.S. Pat. Nos. 4,786,578 (Neisius et al.)(an organic base such as triethanolamine in combination with a non-ionic surfactant); 4,824,762 (Kobayashi et al.) (an ether compound such as dipropyleneglycol monomethyl ether and optionally, an amine compound such as monoethanolamine); and 5,174,816 (Aoyama et al.)(an aqueous solution of a quaternary ammonium hydroxide in combination with a sugar or sugar alcohol). However, the use of such organic solvent-containing rinses are not necessarily desirable because they add complexity to the photoresist removal operation and generate additional solvent waste.
In addition to photoresist residues produced by liquid stripping operations or oxygen gas plasma ashing operations or the like, other residues may form during plasma etching operations used in conjunction with photolithographic processes. For example, as explained in U.S. Pat. No. 5,174,816 (Aoyama et al.) metal halides such as aluminum chlorides may be formed as post-etch residues. Such metal halides may cause corrosion of the substrates when contacted with water.
Furthermore, during anisotropic plasma etching processes for via contacts, metal patterns and possivation openings, post-etch residues may be formed and are know in the art as sidewall polymer residues. After oxygen plasma ashing of the photoresist layer, these sidewall polymer residues become metal oxides. Incomplete removal of these residues interferes with pattern definition and/or complete filling of via holes.
A new class of product called "cleaner solutions" has been developed for removing these post-etch residues, particularly the metal oxide type. These cleaners have generally been described as aqueous solutions of amines or ammonium salts that contain one or more corrosion inhibitors. See U.S. Pat. No. 5,612,304 (Honda et al.). Moreover, alkaline aqueous developers such as those containing tetramethylammonium hydroxide (TMAH) are known to attack aluminum. Thus, aluminum oxide-type residues can be etched away with TMAH. However, other types of the post-etch residues , e.g., metal fluorides such as AlF.sub.3 cannot be so easily removed with TMAH without metal layer corrosion. TMAH also is ineffective on residues from polysilicon plasma etch processes.
The metal oxide type sidewall residues can also be removed with: (1) a mixture of hydrofluoric acid and ethylene glycol ether and water, or (2) a mixture of nitric acid, acetic acid, and hydrofluoric acid. However, these solutions require careful process control to prevent excessive attack of critical metal and oxide layers. In some device structures, these solutions are not useful because of their non-selective attack mechanisms. Also, Wai M. Lee described at Interconnects, Contact Metallization and Multilevel Metallization Symposium (183rd Spring Meeting of The Electrochemical Society) in Honolulu, Hi., May 16-21, 1993, that a hydroxylamine-containing amine/water-based stripper composition can remove some kinds of the sidewall residues.
However, there is still a need for better rinse solutions that can be used after either liquid stripper solutions or the new liquid cleaner solutions (or both), or after a dry oxygen gas plasma ashing operation, that will prevent or inhibit corrosion caused by the reaction of water with the above-noted types of residues, yet not contain organic solvents that require special disposal operations. It is believed the present invention offers a solution to that need.